Sugar helps to preserve platelets

WASHINGTON - A little dab of sugar may double the shelf life of blood platelets, a lifesaving clotting component that is in chronic short supply because of spoilage.

Harvard University researchers report this week in the journal Science that laboratory tests show that putting a small amount of galactose, a type of sugar, into isolated platelets allows the blood components to be refrigerated and usefully preserved for at least 12 days.

That more than doubles the shelf life of the current routine, which is to store the platelets at room temperature for only five days. Because of spoilage, more than 25 percent of all platelets taken from donated blood must be discarded. Extending the shelf life of platelets would significantly improve the supply, experts say.

"If this proves out in clinical trials, this would be an important advance in transfusion medicine," said Dr. Louis M. Katz, medical director of the Mississippi Valley Regional Blood Center in Davenport, Iowa. Katz is president of America's Blood Centers, an organization that collects about half the blood donated in the United States.

Platelets play a central role in forming blood clots, an essential action to prevent uncontrolled bleeding in the body. Platelets are made in the bone marrow and typically live 10 to 12 days in the bloodstream, so the body has to constantly make more platelets to replace those that die.

Many cancer and leukemia patients are unable to naturally replace their platelets. Aggressive chemotherapy used to treat many cancers can cause the bone marrow to shut down, leaving these patients, at least temporarily, without natural platelet replacement.

As a result, about 2-million patients a year require platelet transfusions to avoid possibly lethal, uncontrolled bleeding.

To get enough platelets for a single treatment, blood centers have to process four to six pints of donated blood.

Once they are separated, platelets are very fragile. If they are refrigerated, as whole blood is, the platelets undergo a chemical change that makes them the target of macrophages, one of the body's immune cells. When chilled platelets are transfused, they are engulfed and killed by the macrophages. For this reason, platelets are stored at room temperature and become useless after five days.

Room temperature storage also causes bacteria to grow in warm platelets. Refrigeration, if it was possible, would prevent this.

A team of researchers at Harvard and Brigham and Women's Hospital in Boston have found that platelets can be refrigerated and remain useful for about 12 days if they add a small amount of galactose.

Dr. Karin M. Hoffmeister, first author of the Science study, said macrophages attack chilled platelets because the immune cell targets another type of sugar on the surface of the transfused cell. Adding galactose covers up that other sugar and protects the platelets from the macrophages.